The present invention relates to vent devices which use existing ductwork for reducing the concentration of radon gas and similar undesirable gases in houses and apartments.
Heretofore kitchen, bathroom and other vent fans have been used to vent radon gas from buildings through existing ductwork. The disadvantage of these devices is that they do not act upon radon until after it has permeated the occupancy areas of the house and, therefore, is already a health threat. A device of this type is disclosed in U.S. Pat. No. 3,606,593 and in U.S. Pat. No. 4,681,024. Vents which connect to furnace chimneys must withstand the high temperatures of flue gas, require an experienced installer and may cause poisonous flue gases to leak into the building if not properly maintained. Such a device is disclosed in U.S. Pat. No. 4,543,941.
Additional devices are known in the art. In the known devices sealants are applied to cracks in the building foundation to prevent radon gas from entering. The disadvantage of the above devices is that the sealant is difficult to apply and requires removal of existing floor coverings. Sealants can not be applied in subfreezing temperatures. Sealants rely upon an air tight barrier which has been known to cause the undesirable side effect of increasing the concentrations of other, sometimes toxic, indoor fumes, gases and odors.
An additional known device aims to reduce the concentration of radon below the foundation and thus minimize any inflow to the building. These devices consist of a perforated vent pipe or duct installed beneath the foundation and extending beyond the building walls. Radon gas flows through the path of least resistance from the ground into the pipe and beyond the building walls where it dissipates harmlessly.
The disadvantage of the above device is that it is difficult to retrofit to existing structures. It relys upon the presence of a permeable sub-foundation such as gravel to reliably vent each area of the foundation. This device requires materials, preparation and installation in addition to that which is normally required for a new building as otherwise constructed.